The knock-knock joke is the fad that never died. This form of humor, neither inherent to language like the pun (which it relies heavily upon), nor inherent to human nature like sarcasm must have had a birthdate. At the very least, it could not be older than since man lived behind closed doors. Thankfully, the good folks at Wikipedia had already done their homework on this.
Here are the relevant facts:
- Before the knock-knock joke according to NPR was the “Do You Know?” joke. As in, “Do you know Arthur?” “Arthur Who?” “Arthurmometer!” This sort of nonsense was around at the turn of the 20th century.
- In 1936 the Knock-knock joke took off, appearing everywhere. This undoubtably was the year it became a thing. Also that year that Republicans nominated Col. Frank Knox as their vice-presidential nominee. NPR suggested the two events were not unrelated.
- By the end of that year, it was already annoying, but still it lived on.
- According to a comedy sketch that year, it was invented by a fictional character named Ramrod Dank. I just needed to include that name.